14,888 research outputs found

    A new analysis of 14O beta decay: branching ratios and CVC consistency

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    The ground-state Gamow-Teller transition in the decay of 14O is strongly hindered and the electron spectrum deviates markedly from the allowed shape. A reanalysis of the only available data on this spectrum changes the branching ratio assigned to this transition by seven standard deviations: our new result is (0.54 \pm 0.02)%. The Kurie plot data from two earlier publications are also examined and a revision to their published branching ratios is recommended. The required nuclear matrix elements are calculated with the shell model and, for the first time, consistency is obtained between the M1 matrix element deduced from the analog gamma transition in 14N and that deduced from the slope of the shape-correction function in the beta transition, a requirement of the conserved vector current hypothesis. This consistency is only obtained, however, if renormalized rather than free-nucleon operators are used in the shell-model calculations. In the mirror decay of 14C a similar situation occurs. Consistency between the 14C lifetime, the slope of the shape-correction function and the M1 matrix element from gamma decay can only be achieved with renormalized operators in the shell-model calculation.Comment: 9 pages; revtex4; one figur

    Macroscopic fe-simulation of residual stresses in thermo-mechanically processed steels considering phase transformation effects

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    Residual stresses are an important issue as they affect both the manufacturing processes as well as the performance of the final parts. Taking into account the whole process chain of hot forming, the integrated heat treatment provided by a defined temperature profile for cooling of the parts offers a great potential for the targeted adjustment of the desired residual stress state. However, in addition to elastic, plastic and linear thermal strain components, the complex material phenomena arising from phase transformation effects of the polymorphic steels have to be considered in order to predict the residual stresses. These transformation strains account for the plastic deformation at the phase boundary between the emerging and the parent phase. In addition, they are strongly related to the transformation induced plasticity (TRIP) phenomena which depend on the stress state. The aim of this study is the investigation of TRIP effects and their impact on residual stresses regarding the typical hot forming steels 1.7225 (DIN: 42CrMo4) and 1.3505 (DIN: 100Cr6) by means of an experimental-numerical approach. The TRIP behaviour of the materials under consideration is integrated into an FE simulation model in the commercial software Simufact.forming for the purpose of residual stress prediction. The experimental thermo-mechanical investigations are carried out using a quenching and forming dilatometer. These experiments are numerically modelled by means of FEM which allows TRIP coefficients to be determined phasespecifically by numerical identification. For validation of the improved FE-model, an experimental thermo-mechanical reference process is considered, in which cylindrical specimens with an eccentric hole are hot formed and subsequently cooled by different temperature routes. Finally, the numerical model is validated by means of a comparison between residual stress states determined with X-ray diffraction and predicted residual stresses from the simulation

    The impact of Lyman-α\alpha radiative transfer on large-scale clustering in the Illustris simulation

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    Lyman-α\alpha emitters (LAEs) are a promising probe of the large-scale structure at high redshift, z2z\gtrsim 2. In particular, the Hobby-Eberly Telescope Dark Energy Experiment aims at observing LAEs at 1.9 <z<<z< 3.5 to measure the Baryon Acoustic Oscillation (BAO) scale and the Redshift-Space Distortion (RSD). However, Zheng et al. (2011) pointed out that the complicated radiative transfer (RT) of the resonant Lyman-α\alpha emission line generates an anisotropic selection bias in the LAE clustering on large scales, s10s\gtrsim 10 Mpc. This effect could potentially induce a systematic error in the BAO and RSD measurements. Also, Croft et al. (2016) claims an observational evidence of the effect in the Lyman-α\alpha intensity map, albeit statistically insignificant. We aim at quantifying the impact of the Lyman-α\alpha RT on the large-scale galaxy clustering in detail. For this purpose, we study the correlations between the large-scale environment and the ratio of an apparent Lyman-α\alpha luminosity to an intrinsic one, which we call the `observed fraction', at 2<z<62<z<6. We apply our Lyman-α\alpha RT code by post-processing the full Illustris simulations. We simply assume that the intrinsic luminosity of the Lyman-α\alpha emission is proportional to the star formation rate of galaxies in Illustris, yielding a sufficiently large sample of LAEs to measure the anisotropic selection bias. We find little correlations between large-scale environment and the observed fraction induced by the RT, and hence a smaller anisotropic selection bias than what was claimed by Zheng et al. (2011). We argue that the anisotropy was overestimated in the previous work due to the insufficient spatial resolution: it is important to keep the resolution such that it resolves the high density region down to the scale of the interstellar medium, 1\sim1 physical kpc. (abridged)Comment: 11 pages, published in A&

    Success Factors for an E-Government Strategy: Austrian Experiences, Indonesian Challenges

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    Focus of this paper are success factors for the implementation of an E-Government strategy. Whileconcepts for a sophisticated strategy process in Public Sector are delivered on a regular basis, the gapbetween ambitious planning and its implementation seems to get wider. Authors seek to define whatmakes a “good strategy” in order to enhance management capacity. Meanwhile some scholars fromPolitical Science see limitation of Governments on announcements which are not followed up bysufficient action rather as systematic problems, challenging concept and rules of liberal westerndemocracy, or owed to growing complexity of Governance under the conditions of globalization. Incontext of the introduction of New Public Management and its perception of citizens as customers andon the basis of new available technical options in Information Society, a key Governance reform projectin European and other Countries over the last fifteen years has been the introduction of E-Government.European market leader in this field is Austria. The author reviews concept and implementationexperiences of the Austrian E-Government strategy, analyzes key success factors and opens adiscussion, under which conditions a successful implementation of E-Government can take place inIndonesia

    Usage-based and emergentist approaches to language acquisition

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    It was long considered to be impossible to learn grammar based on linguistic experience alone. In the past decade, however, advances in usage-based linguistic theory, computational linguistics, and developmental psychology changed the view on this matter. So-called usage-based and emergentist approaches to language acquisition state that language can be learned from language use itself, by means of social skills like joint attention, and by means of powerful generalization mechanisms. This paper first summarizes the assumptions regarding the nature of linguistic representations and processing. Usage-based theories are nonmodular and nonreductionist, i.e., they emphasize the form-function relationships, and deal with all of language, not just selected levels of representations. Furthermore, storage and processing is considered to be analytic as well as holistic, such that there is a continuum between children's unanalyzed chunks and abstract units found in adult language. In the second part, the empirical evidence is reviewed. Children's linguistic competence is shown to be limited initially, and it is demonstrated how children can generalize knowledge based on direct and indirect positive evidence. It is argued that with these general learning mechanisms, the usage-based paradigm can be extended to multilingual language situations and to language acquisition under special circumstances

    Paying for Status? - The effect of frequent flier program member status on air fare choice

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    Frequent flier programs (FFPs) are said to affect airline customer behaviour such that revenue of sponsoring airlines increases. To this end prior research relies on assumptions of competition, lock-in effects and variations in scale and scope of FFPs. Whether a FFP by itself induces a price premium remains unanswered. In an effort to shine some light on this question, we apply discrete choice analysis to a new proprietary data set of actual frequent flier member flight behaviour (fares paid, FFP points received) over a 12-months period. We take advantage of the variations in the structure of FFPs (Gold, Silver and Bronze tier levels), to assess both the existence of a FFP price premium and the price premiums average monetary value in US$ per FFP member. Our findings suggest that FFP members are willing to pay a price premium of up to six percent, which is directly attributable to the FFP.discrete choice analysis, loyalty programs, relationship marketing, price premium, frequent flier program, CRM

    CO line emission from galaxies in the Epoch of Reionization

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    We study the CO line luminosity (LCOL_{\rm CO}), the shape of the CO Spectral Line Energy Distribution (SLED), and the value of the CO-to-H2\rm H_2 conversion factor in galaxies in the Epoch of Reionization (EoR). To this aim, we construct a model that simultaneously takes into account the radiative transfer and the clumpy structure of giant molecular clouds (GMCs) where the CO lines are excited. We then use it to post-process state-of-the-art zoomed, high resolution (30pc30\, \rm{pc}), cosmological simulation of a main-sequence (M1010MM_{*}\approx10^{10}\, \rm{M_{\odot}}, SFR100Myr1SFR\approx 100\,\rm{M_{\odot}\, yr^{-1}}) galaxy, "Alth{\ae}a", at z6z\approx6. We find that the CO emission traces the inner molecular disk (r0.5kpcr\approx 0.5 \,\rm{kpc}) of Alth{\ae}a with the peak of the CO surface brightness co-located with that of the [CII] 158μm\rm \mu m emission. Its LCO(10)=104.85LL_{\rm CO(1-0)}=10^{4.85}\, \rm{L_{\odot}} is comparable to that observed in local galaxies with similar stellar mass. The high (Σgas220Mpc2\Sigma_{gas} \approx 220\, \rm M_{\odot}\, pc^{-2}) gas surface density in Alth{\ae}a, its large Mach number (\mach30\approx 30), and the warm kinetic temperature (Tk45KT_{k}\approx 45 \, \rm K) of GMCs yield a CO SLED peaked at the CO(7-6) transition, i.e. at relatively high-JJ, and a CO-to-H2\rm H_2 conversion factor αCO1.5M(Kkms1pc2)1\alpha_{\rm CO}\approx 1.5 \, \rm M_{\odot} \rm (K\, km\, s^{-1}\, pc^2)^{-1} lower than that of the Milky Way. The ALMA observing time required to detect (resolve) at 5σ\sigma the CO(7-6) line from galaxies similar to Alth{\ae}a is 13\approx13 h (38\approx 38 h).Comment: 16 pages, 14 figures, accepted for publication in MNRA

    Viscosity, pressure, and support of the gas in simulations of merging cool-core clusters

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    Major mergers are considered to be a significant source of turbulence in clusters. We performed a numerical simulation of a major merger event using nested-grid initial conditions, adaptive mesh refinement, radiative cooling of primordial gas, and a homogeneous ultraviolet background. By calculating the microscopic viscosity on the basis of various theoretical assumptions and estimating the Kolmogorov length from the turbulent dissipation rate computed with a subgrid-scale model, we are able to demonstrate that most of the warm-hot intergalactic medium can sustain a fully turbulent state only if the magnetic suppression of the viscosity is considerable. Accepting this as premise, it turns out that ratios of turbulent and thermal quantities change only little in the course of the merger. This confirms the tight correlations between the mean thermal and non-thermal energy content for large samples of clusters in earlier studies, which can be interpreted as second self-similarity on top of the self-similarity for different halo masses. Another long-standing question is how and to which extent turbulence contributes to the support of the gas against gravity. From a global perspective, the ratio of turbulent and thermal pressures is significant for the clusters in our simulation. On the other hand, a local measure is provided by the compression rate, i.e. the growth rate of the divergence of the flow. Particularly for the intracluster medium, we find that the dominant contribution against gravity comes from thermal pressure, while compressible turbulence effectively counteracts the support. For this reason it appears to be too simplistic to consider turbulence merely as an effective enhancement of thermal energy.Comment: 16 pages, 16 figures, accepted for publication by MNRA

    Phase relations for water and ice in confined geometry

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    A brief survey is given of the structural characteristics of water at low temperatures in the normal and super-cooled states using neutron diffraction. Similar studies axe presented for D2O water in mesoporous sol-gel silicas showing the depression of the nucleation temperature, the effects of fractional filling and the formation of cubic ice I-c in the pores. Preliminary data is also presented for both neutron and x-ray diffraction studies of water in the ordered MCM41 silica, showing the deep super-cooling and the reversible phase transformation between water and cubic ice. The importance of hydrogen-bonded networks and the development of long-range correlations axe used to provide an explanation of the observations. Further work is in progress

    A population-based case-control study on social factors and risk of testicular germ cell tumours

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    Objectives Incidence rates for testicular cancer have risen over the last few decades. Findings of an association between the risk of testicular cancer and social factors are controversial. The association of testicular cancer and different indicators of social factors were examined in this study.&lt;p&gt;&lt;/p&gt; Design Case–control study.&lt;p&gt;&lt;/p&gt; Setting Population-based multicentre study in four German regions (city states Bremen and Hamburg, the Saarland region and the city of Essen).&lt;p&gt;&lt;/p&gt; Participants The study included 797 control participants and 266 participants newly diagnosed with testicular cancer of which 167 cases were classified as seminoma and 99 as non-seminoma. The age of study participants ranged from 15 to 69 years.&lt;p&gt;&lt;/p&gt; Methods Social position was classified by educational attainment level, posteducational training, occupational sectors according to Erikson-Goldthorpe-Portocarrero (EGP) and the socioeconomic status (SES) on the basis of the International SocioEconomic Index of occupational status (ISEI). ORs and corresponding 95% CIs (95% CIs) were calculated for the whole study sample and for seminoma and non-seminoma separately.&lt;p&gt;&lt;/p&gt; Results Testicular cancer risk was modestly increased among participants with an apprenticeship (OR=1.7 (95% CI 1.0 to 2.8)) or a university degree (OR=1.6 (95% CI 0.9 to 2.8)) relative to those whose education was limited to school. Analysis of occupational sectors revealed an excess risk for farmers and farm-related occupations. No clear trend was observed for the analyses according to the ISEI-scale.&lt;p&gt;&lt;/p&gt; Conclusions Social factors based on occupational measures were not a risk factor for testicular cancer in this study. The elevated risk in farmers and farm-related occupations warrants further research including analysis of occupational exposures.&lt;p&gt;&lt;/p&gt
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